When McLaren-Honda announced that star driver Fernando Alonso was going to skip the Monaco Grand Prix to contest the Indianapolis 500, it caused a major stir. A double world champion skipping Formula 1’s crown jewel to race in America? The news surprised – shocked – almost everyone. But not Mario Andretti.

“I remember Fernando mentioning Indianapolis to me two years ago at Monza,” the American racing legend tells Autocar. “We were chatting about something, and he brought Indianapolis up out of the blue. You could tell it was in his mind even then. He didn’t just start thinking about the Indy 500 a month ago.”

If Alonso has been plotting an outing in ‘The Greatest Spectacle in Racing’ for so long, picking Andretti’s brain was a great place to start. Andretti is one of an elite group of drivers to have won both the Indy 500 (in 1969) and the Formula 1 world championship (in 1978).

In fact, Andretti is one of motorsport’s truly great all-rounders. As well as F1 and Indycar, Andretti raced on dirt ovals and in sports cars, NASCAR and drag racing. And he won in just about every category. “The challenge is to go in somebody else’s sandbox and try to win at their own game,” he says. “That’s the ultimate satisfaction, and that’s what Fernando is trying to do. That’s healthy. His mindset is not just to go to Indy and get a feel for things – he’s thinking about winning. And you have to have that mindset to have a chance to do that.

“He’s enjoying himself. It’s too bad he has the circumstances he does in F1, which aren’t very appealing at the moment, but it’s good he could do this without feeling he’s giving anything up there. We all know if he could have been competitive in Monaco he wouldn’t be doing this. So it’s great that he’s taking advantage of this moment.”

While the McLaren-Andretti-Honda Dallara DW12 that Alonso is driving this week looks somewhat similar to an F1 car, the Indianapolis 500 will be unlike any race Alonso has tackled before. The Indianapolis Motor Speedway is a high-speed 2.5-mile oval where average speeds can push 230mph. Make a mistake and the walls are unforgiving. And with incredible parity between the 33 machines that will take part in Sunday’s race, Alonso will be racing wheel-to-wheel for most of the 200 laps.

Despite that, Andretti says a driver of Alonso’s talents will have little trouble adjusting. So what are the secrets of switching categories? “Obviously there are differences in the animal you’re trying to deal with, but the whole trick is to get yourself into good equipment with a top team,” he says. “That’s something I was blessed with – I moved from discipline to discipline with top teams, and that’s why I had good results. If Fernando came over with a lesser team, he wouldn’t go away very happy.

“You can’t perform miracles. Put Fernando in a Mercedes or Ferrari in F1 right now and he’d score results. But put him in a McLaren, and I don’t care how good he is, he can’t get results. You can only be happy if you move around and know you can get good results. It’s not about being there for the experience.”

When Andretti talks about Alonso coming over with a top team, he might be a bit biased: the Andretti Autosport outfit that will run Alonso’s McLaren-badged entry (bizarrely labelled as a McLaren-Honda Andretti-Honda on official entry lists) is owned by Mario’s son Michael, a former McLaren F1 driver himself.

But the team is, undoubtedly, one of the best in the business. And Alonso’s five team-mates this weekend will include 2012 IndyCar Series champion Ryan Hunter-Reay, ex-F1 racer Takuma Sato and last year’s Indy 500 winner and ex-F1 racer Alexander Rossi. With the team having an open data policy, Alonso will have a wealth of information and experience to draw upon.

“Michael’s team will do everything they can to give Fernando an opportunity to score well,” says Andretti. “And he’ll have five drivers to draw data from. I don’t remember ever, ever, ever having anything close to that information. I remember going to NASCAR and nobody would even talk to me, let alone give me information. I was welcome to come and race, but nobody was willing to open up and help me go fast.”

That included the Ford-backed Holman Moody team Andretti drove for when he won the 1967 Daytona 500 – one of just three NASCAR races he competed in. At one stage they held him in the pits to hand the lead to regular driver Fred Lorenzen – yet Andretti still won.

“I felt very alone, in that respect,” recalls Andretti. “But that’s the way the culture was then. Michael runs his team differently. As a veteran driver, I’m not sure I’d welcome that – I always had proprietary knowledge that I liked to keep to myself.”

While Alonso is switching – albeit as a one-off – from F1 to Indy, Andretti went the other direction in his career. Italian-born Andretti’s motorsport passion began watching grand prix racing at Monza before his family emigrated to the USA in 1955. He began racing on Pennsylvania’s dirt ovals, but always dreamed of reaching F1.

It was as an Indy 500 rookie, in 1965, that Andretti built his first links to F1. The dominant winner of that year’s event was Jim Clark, running in a works Lotus, part of a mid-1960s F1 invasion that sparked a switch from front to rear-engined racing cars at the Brickyard (notably, Clark skipped the Monaco Grand Prix to race at Indy that year).

“All I wanted to do was meet [Lotus boss] Colin Chapman and Jim," Andretti says. "I did well as a rookie in the race, and that last word I had with Colin was ‘some day I’d like to do F1.’ He said ‘when you’re ready, call me.’

“I came away that year feeling good, and challenged myself to get road racing experience. When it was time for my first Formula 1 grand prix [the 1968 US Grand Prix at Watkins Glen in a Lotus-Ford] I qualified on pole.

“In comparison to an IndyCar at that time, the F1 car felt so right, so perfect. But when a car feels good you don’t care what it is – you feel good and go fast.”

After occasional outings with Lotus between 1968 and 1970, Andretti switched to Ferrari, winning his first grand prix in South Africa in 1971. He also drove for American team Parnelli but returned to Lotus in 1976, and in 1978 won six races on his way to the world championship.

Defining Indy 500 success for Alonso

Can Alonso emulate Clark’s victorious switch? “Clark had a big advantage with the car,” says Andretti. “Lotus came here with a clear advantage and took the top prize. Alonso will find the competition a lot closer.

“A huge result for him would be a top five. That could be equal to a win, it would be an enormous result. A top ten would still be a good result.”

Andretti’s words are a reminder that no matter grand Alonso’s F1 CV is – two world titles, 32 race wins, 97 podiums and 22 pole positions – he’s still an oval racing rookie, and the Indy 500 is a tough race to win. That’s something Andretti knows well: for all his success, he only won the Indy 500 once, in 1969. His son Michael, the 1991 IndyCar champion, never won it, either, and so far his grandson Marco – an IndyCar Series race winner – has yet to break what’s become known as the ‘Andretti curse’.

How important is an Indy 500 win to a driver’s CV? “The importance of the race? Sometimes it’s actually unfair,” says Andretti. “I’ve dominated that race more than four-time winners, but I wasn’t lucky in the final part - to be able to finish.

“Sometimes if you paced yourself and didn’t really charge, that paid off. But I was never that type of driver. I was always ten-tenths, and I paid the price for that. I’m third in all-time laps led in the Indy 500. But that’s my prize: I dominated that race enough times to give me the satisfaction. I don’t have the rings to show for it, but I’m not ashamed of that.”

That leaves one final question: how important would an improbable Indy 500 win be to Alonso’s career? The answer to that goes back to that conversation Andretti had with Alonso at Monza two years ago. This is a personal mission for the Spaniard – but one being played out on a worldwide stage.

“It’s whatever melts your butter, whatever turns you on,” says Andretti. “It’s a lot of extra work – look at what Fernando’s been through just in terms of travel – and a big effort, but the reward can be nice. And he’s doing it for that ultimate reward.”

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Join the debate

The word 'legend' is often mis-used, but in the case of Mario Andretti it is entirely appropriate.

This is a guy who, as the article rightly points out, has raced in many, many categories of motorsport - add in, he's won in pretty much every one of them.

The fact that by all contemporary accounts he's one of the nicest guys out there, completely down to earth, has a colourful and amusing turn of phrase, still lives in the town his family arrived at in the USA in the early 50s, when with his success he could be living anywhere in the world - merely adds to his credit.

A lot of the current crop of sports-stars both in and out of motorsport could learn a heck of a lot from Mario.